This invention generally relates to a method for manufacturing a pile fabric with pile loops formed by coarse pile threads. In particular this invention relates to a new method for manufacturing carpets, whereby coarse pile warp threads are used, such as for example the type of carpets with a low pile row density that up until now are manufactured by means of an Axminster weaving machine. In that which follows, these carpets are referred to as Axminster carpets.
The known Axminster gripper weaving machines are provided with a weft insertion mechanism for inserting weft threads between warp threads so that a backing fabric is formed, with a pile gripper mechanism with several up and down rotatable pile grippers, and with pile loaders in which a number of pile warp threads are provided one above the other and can be fed to the pile grippers. Prior to each weft insertion the pile warp threads with the desired color (corresponding to the pattern to be woven) can be brought to the respective pile grippers by means of a jacquard mechanism, if these pile grippers are rotated to their top position. During the downward rotation of the pile grippers the pile warp threads are pulled over a specific length out of the loader. The pulled-out part of the respective pile warp threads is cut off, is brought to the fabric edge by the further downward movement of the pile grippers, and is there held in an inweaving position in order finally after insertion of weft threads to be woven into the backing fabric as a pile loop.
The pile grippers disposed one next to the other must have a minimum thickness in order to have sufficient stability. This results in the reed density having to be maintained rather low with Axminster weaving machines. Generally this reed density is limited to at most 7 per inch (276/meter). Exceptionally reed densities from 8 to 10 per inch are also utilized, but even in those cases pile fabrics with a rather low pile row density are obtained.
In order nevertheless to obtain a certain volume of pile yarn with the pile fabrics which are woven with these Axminster weaving machines, rather thick pile yarns are usually used. Preferably pile yarns of the carded type are used in a yarn number range from Nm 3.2/2 to Nm 3.6/2.
A disadvantage of the known methods for manufacturing pile fabrics with pile loops formed by coarse pile threads lies in the fact that the Axminster weaving machines used for that purpose run rather slowly because of their mechanical complexity. The productivity of the known methods is consequently rather low.
It has been attempted to remedy the above mentioned disadvantage by using face-to-face weaving machines. The operating speed of these weaving machines (e.g. 120 revolutions per minute) indeed lies much higher than the Axminster weaving machines (e.g. 65 revolutions per minute). Furthermore the weft insertion mechanism of these weaving machines is provided for simultaneously inserting two weft threads in each case in successive insertion cycles.
When manufacturing a pile fabric on a face-to-face weaving machines a top and a bottom backing fabric are woven by inserting weft threads in sheds formed between warp threads, while pile-forming pile warp threads are so positioned in relation to the weft insertion levels that these are alternately passed round one or several weft threads in the top and in the bottom backing fabric. The pile-forming pile warp threads are afterwards cut through between the two backing fabrics so that two pile fabrics are obtained.
Manufacturing a pile fabric with pile loops formed by coarse pile threads on a face-to-face weaving machines, such as for example an Axminster carpet, appeared however until now to be impossible. The coarse pile warp threads indeed appeared not be weavable on face-to-face weaving machines because with the shed formation they entangle with each other too easily. This results in a shed which is not perfectly formed. Because of this pile warp threads are damaged or torn off by a weft insertion means moving in the shed, and inwoven non-pile-forming pile warp threads are upset so that they form unwanted pile loops both along the back and along the pile side of the fabric. Because of this it was until now considered impossible to weave pile fabrics with coarse pile warp threads, such as for example Axminster carpets, on face-to-face weaving machines in order to increase the productivity.